This invention relates to an alumina composite body and a method for its manufacture, particularly to an alumina composite body comprising alumina, aluminum and silicon.
Alumina ceramic materials have excellent hardness, mechanical strength, heat resistance and chemical stability. Their heat resistance is not inferior to that of other ceramic materials such as silicon carbide and silicon nitride. In addition, alumina ceramic materials are inexpensive, so that alumina ceramic materials are widely used as industrial ceramic materials as described by Japanese Published Patent Application No. 54-87716.
Conventionally, alumina ceramic products are made by forming fine alumina particles into desired shape and then firing the formed shape, or by forming and firing fine alumina particles at the same time as described by Japanese Published Patent Application No. 57-95870 or Japanese Patent Publication No. 59-25748. As shown in FIG. 1, a conventional alumina ceramic material constitutes alumina particles 21 having a simple shape.
Conventional alumina ceramic materials have the following disadvantages:
(1) The workability is bad due to their hardness. PA1 (2) The shock resistance is low because of their brittleness. Generally speaking, the shock break resistance of ceramic materials is inferior to that of metals. PA1 (3) It is difficult to exactly form any complex shapes of alumina ceramic products. PA1 (4) The firing temperature is a high temperature on the order of from 1500.degree. to 1900.degree. C. PA1 (5) The shrinkage on firing is large. PA1 (6) The thermal shock resistance is low. PA1 (7) The lubricity is inferior to that of the metals.
Although alumina ceramic materials have many excellent basic characteristics, because of these disadvantages they cannot be used satisfactorily as structural materials which must satisfy severe strength and mechanical reliability requirements.